Memory Leak Playground

These are my personal notes for myself to help with future debugging. Every new or malloc in C++ requires a delete/delete[] or free. Not deallocating allocated stack memory results in memory leaks.

TL;DR

1. Build the project from the project root or using IDE: make build
2. Run the program from the command line: make run or ./cmake-build-debug/app/my_app
3. Open another Tmux pane and run Top to see memory usage: top -p $(ps -aux | grep my_app | head -n 1 | awk '{print $2}')
4. Press E to see memory usage in mb in Top.
5. Run Valgrind to find the memory leak: valgrind --leak-check=full ./my_app

Valgrind

Valgrind displays memory leaks in programs. Running valgrind FILE shows how much memory, if any, was leaked:

Running Valgrind with --leak-check=full reveals the place where the memory leak may be happening and the stack trace:

After fixing the leak, running Valgrind again displays the happy news:

Top

Top displays Linux processes, but it's not so helpful to run by itself - processes shift around and it's hard to keep track of the one you want:

We can use the -p switch and pass Top the PID to watch just our app running:

Finding the process each time is repetitive, so we can filter out the PID from the list of processes using:

ps -aux | grep my_app | head -n 1 | awk '{print $2}'

Together with the previous command we get:

top -p $(ps -aux | grep my_app | head -n 1 | awk '{print $2}')

Which displays the memory usage of the app with the new PID each time Top is run. Now press E to see the memory displayed in different formats, e.g. MB, GB, TB, etc.